What is the condition of the three remaining bearings??? Are they old ... dis-colored ... cracked ... brittle ... rough feeling ... have flat spots ... any or all of the above???

If the answer is yes to any of the previous questions .... replace. The delran bearings are not that expense. Your time to re-build the boom is much more valuable/costly then the actual cost of the replacement bearings ..... that's why I've developed a general philosophy of not re-using "old/used" 1/2 way worn-out parts, unless I have no other option at that moment ....

Especially on a boat ... "where failure is not a option ...."

... as it is not a option/occurance I usually enjoy having to deal w/ when I'm out boating/sailing .... usually ruining the "karma" of the moment ... and could also have dire consequences ....